Chemical mechanical polishing system and process

ABSTRACT

Chemical mechanical polishing (CMP) systems and methods are provided herein. One aspect of the present subject matter is a polishing system. One polishing system embodiment includes a platen adapted to receive a wafer, and a polishing pad drum that has a cylindrical, or generally cylindrical, shape with a length and an axis of rotation along the length. The polishing pad drum is adapted to rotate about the axis of rotation along the drum length. The polishing pad drum, the platen, or both the polishing pad drum and the platen are adapted to be linearly moved to polish the surface of the wafer using the rotating polishing pad drum. The polishing pad drum and the platen are adapted to be operably positioned a predetermined minimum distance from each other as the polishing pad drum and the platen pass each other due the linear motion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/485,198, filed Jul. 12, 2006, which is a continuation of U.S. patentapplication Ser. No. 09/944,983, filed Aug. 30, 2001, now issued as U.S.Pat. No. 7,121,919, which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to semiconductor processing and, moreparticularly, to chemical mechanical polishing systems and processes.

BACKGROUND OF THE INVENTION

One problem that is confronting the semiconductor processing industry inthe age of ultra large scale integration (ULSI) is capacitive-resistanceloss in wiring levels. Conventionally, aluminum and aluminum alloys havebeen used for semiconductor wiring. In an effort to improveconductivity, it has been suggested to substitute copper metallurgy foraluminum metallurgy.

However, problems have been encountered in developing copper metallurgy.One problem is that copper quickly diffuses through both silicon andsilicon dioxide (SiO₂). Another problem is the known junction poisingeffects of copper. It has been proposed to use a liner to separate thecopper metallurgy from the SiO₂ insulator. Proposed liners includeeither a metal such as tantalum (Ta) or tungsten (W), or a compound suchas tantalum nitride (TaN) or silicon nitride (Si₃N₄). Another problem isthat copper, unlike aluminum, does not form a volatile compound at roomtemperature and thus cannot be reactively ion etched. The “damascene”process has been used to form copper lines embedded in an insulator. Inthis process, a layer of insulator is deposited, and trenches forconductors are formed in the insulator using a reactive ion etching(RIE) process. A liner and adhesion layer is deposited, and copper isblanket deposited by either chemical vapor deposition (CVD) orelectroplating. The unwanted copper and liner is then removed by achemical mechanical polishing (CMP) process.

CMP is a semiconductor wafer flattening and polishing process thatcombines the chemical removal of semiconductor layers such as insulatorsand metals with the mechanical buffing of a wafer surface. Typically,CMP is used to polish or flatten wafers after crystal growing during thewafer fabrication process, and to polish or flatten the profiles thatbuild up in multilevel metal interconnection schemes.

A traditional CMP tool has a hard surface platen onto which the wafer isfixed. A polishing abrasive is applied and a polishing pad, which maycontain additional abrasive, is moved over the wafer surface. Thepolishing solution containing the abrasive is, at least to some extent,generally reactive to the materials being polished. In one knownpolishing system, the abrasive is fixed to the pad and the pad isimmersed in a liquid. This pad is then used in a similar method as theother systems.

In many CMP systems, the wafer platen and the polishing pad are rotatedduring the polishing process. Some designs have used a belt thatcontains an abrasive material. These systems have been used to achieve asignificant degree of local planarization as well as limited long rangeplanarization. However the degree of long range planarization has beensignificantly less than desired. Additionally, other non uniformityproblems such as dishing and rounding of the features tend to occur.These non uniformity problems result in uneven surfaces and layers thatare not uniformly thick. This is a significant problem for achievingcomplete planarization.

Therefore, there is a need in the art to provide a CMP system andprocess that overcomes the problems of uneven surfaces and increases thedegree of long range planarization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one chemical mechanical polishing (CMP)system embodiment.

FIG. 2 is top view of the CMP system of FIG. 1.

FIG. 3 is a front view of the CMP system of FIG. 1.

FIG. 4 is a cross-section view along line 4-4 of the CMP system shown inFIG. 3.

FIG. 5 is a block diagram of one CMP system embodiment.

FIG. 6 is a side view of the CMP system of FIG. 5, illustrating themotion of the drum and the platen.

FIG. 7 is a block diagram of one CMP system embodiment.

FIG. 8 is a side view of the CMP system of FIG. 7, illustrating themotion of the drum and the platen.

FIG. 9 is a block diagram of one CMP system embodiment.

FIG. 10 is a side view of the CMP system of FIG. 9, illustrating themotion of the drum and the platen.

FIG. 11 is a block diagram of one CMP system embodiment.

FIG. 12 is a block diagram of another CMP system embodiment.

FIG. 13 is a block diagram of one embodiment of an electronic systemused as a controller for a CMP system.

FIG. 14 is a flowchart illustrating one embodiment of a semiconductorprocess that incorporates one embodiment of a CMP process.

FIG. 15 is a flowchart illustrating one embodiment of a process forremoving a semiconductor layer.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of the invention refers to theaccompanying drawings which show, by way of illustration, specificaspects and embodiments in which the invention may be practiced. In thedrawings, like numerals describe substantially similar componentsthroughout the several views. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe present invention. The following detailed description is, therefore,not to be taken in a limiting sense, and the scope of the presentinvention is defined only by the appended claims, along with the fullscope of equivalents to which such claims are entitled.

The present subject matter provides chemical mechanical polishing (CMP)systems and methods in which a rotating polishing pad drum is used topolish a wafer held by a platen. The polishing pad drum operablycontacts the wafer through a relative linear movement between the waferand the rotating polishing pad drum. The linear motion is characterizedas being perpendicular (albeit in a different plane) to the axis ofrotation of the polishing drum, which significantly increasing thedegree of long range planarization by reducing uniformity problems suchas dishing and rounding of the features.

FIG. 1 is a perspective view of one chemical mechanical polishing (CMP)system embodiment. The illustrated embodiment of the CMP system 100includes a platen 102 and a polishing pad drum 104.

According to one embodiment, the polishing pad drum 104 is formed in theshape of a cylinder or drum. According to another embodiment, thepolishing pad drum 104 includes a drum center and a polishing padattached around the drum center.

According to one embodiment, the polishing pad drum 104 is rigid. Inthis embodiment, for example, a soft backing material is not used in thepolishing pad.

A CMP process uses a polishing agent that is, at least to some extent,generally reactive to the materials being processed. According to oneembodiment, a polishing abrasive is embedded in the polishing pad drum104. Another embodiment provides the polishing abrasive separately in aslurry.

A semiconductor wafer 106 is placed on or is otherwise received by theplaten 102. The polishing pad drum 104 has a length that preferablyspans across the width of the wafer 106. The polishing pad drum 104 hasan axis of rotation 108 along the length of the polishing pad drum 104.A motor drive 110 rotates the polishing pad drum 104 about the axis ofrotation 108. By having a length that spans across the entire width ofthe wafer 106, the rotating polishing pad drum 104 is able to processthe entire wafer 106 in one pass.

The polishing pad drum 104 and the platen 102 are adapted to have arelative linear movement with respect to each other. In the illustratedCMP system 100, the relative linear motion is represented by arrow 112.According to one embodiment, the platen 102 is moved in the direction ofarrow 112 to provide the relative linear motion. As will be apparent toone of ordinary skill in the art upon reading and understanding thisdisclosure, the CMP system 100 may be designed such that the relativelinear motion between the platen 102 and the polishing pad drum 104 maybe achieved by moving the platen 102 as shown, by moving the polishingpad drum 104, or by moving both the polishing pad drum 104 and theplaten 102.

If the directional vector represented by the arrow 112 and the axis ofrotation 108 of the polishing pad drum 104 were coplanar, thedirectional vector 112 would be perpendicular, or generallyperpendicular, to the axis of rotation 108. That is, a projection of thedirection vector 112 onto a parallel plane that includes the axis ofrotation 108 is perpendicular, or generally perpendicular, to the axisof rotation.

It is noted that there is a predetermined separation between the platen102 and the polishing pad drum 104 such that the wafer 106 can fitbetween the platen 102 and polishing pad drum 104 for a CMP process.This predetermined separation can be characterized as a predeterminedminimum distance between the polishing pad drum 104 and the platen 102as the polishing pad drum 104 and the platen 102 pass each other due tothe linear motion. In other words, there is a distance between thepolishing pad drum 104 and the platen 102. As the polishing pad drum 104and the platen 102 move toward each other, the distance between the twobecomes less and less until they are a predetermined minimum distancefrom each other.

The rotation of the polishing pad drum 104 produces a tangential forcebetween the platen 102 and the polishing pad drum 104. The rotation ofthe polishing pad drum is represented by arrow 116. This tangentialforce represents the polishing force produced by a wafer contact portion114 of the rotating polishing pad drum 104. According to one embodiment,the direction of the rotation of the polishing pad drum 104 is such thatthe tangential force between the platen 102 and the polishing pad drum104 is in the same direction as the motion of the platen 102. In thisembodiment, any debris produced by the CMP process is thrown in adirection so as not to interfere with the ongoing CMP process; that is,the debris is not thrown toward the unprocessed portions of the wafer106. The direction, speed and timing of the motions may be varied forvarious CMP system designs.

The illustrated embodiment of the CMP system 100 also includes aplanarizing system 118 used to dress the polishing pad drum 104.According to one embodiment, the planarizing system 118 includes a laserthat has a finely tuned laser beam 120 to appropriately dress thesurface of the polishing pad drum 104. Dressing the surface of thepolishing pad drum 104 involves providing the cylindrically-shapedpolishing pad drum 104 with a smooth or uniform surface such that thepolishing pad drum 104 has a uniform diameter along its length.

FIG. 2 is top view of the CMP system of FIG. 1. The system 200 includesa platen 202, a polishing pad drum 204, a motor drive 210 and aplanarizing system 218. In this view of the embodiment, the wafer 206 isbeing carried by the platen 202 underneath the polishing pad drum 204.The motor drive 210 rotates the polishing pad drum 204 in a directionthat throws debris from a CMP process in a direction along the linearmovement of the platen 202 such that the debris will not interfere withthe ongoing CMP process. The planarizing system 218 includes a laserthat has a laser beam 220 that is adapted to dress the polishing paddrum 204 as needed. According to this embodiment, the relative positionbetween the drum 204 and the beam 220 is changed during operation andthe magnitude of the change is sensed by the controller.

FIG. 3 is a front view of the CMP system of FIG. 1. In this view, thewafer 306 is shown as being disposed in between the platen 302 and thepolishing pad drum 304. The wafer 306 is shown as being moved by theplaten 302 into the page.

FIG. 4 is a cross-section view along line 4-4 of the CMP system shown inFIG. 3. In this view, the wafer 406 is shown as being disposed inbetween the platen 402 and the polishing pad drum 404. The wafer 406 isshown as being moved by the platen 402 to the right. It is apparent fromthis view of this embodiment that the debris from the CMP process isdirected in the direction of relative motion of the wafer 406 withrespect to the polishing pad drum 404.

FIG. 5 is a block diagram of one CMP system embodiment. According tothis embodiment, the CMP system 500 includes a platen 502 and apolishing pad drum 504. The platen 502 is adapted to be linearly moved,and the polishing pad drum 504 is adapted to be rotationally moved. Aplaten drive assembly 522 controls the linear movement of the platen anda drum drive assembly 524 controls the rotational movement of thepolishing pad drum 504. A controller 526 is coupled to and incommunication with the platen drive assembly 522 and the drum driveassembly 524 and the planarizing system 518 which, according to oneembodiment, includes a trimming laser.

As is apparent to one of ordinary skill in the art, the controller 526may be hardware, software, or a combination thereof. The controller 526controls the operation of the drive assemblies 522 and 524, and thus themovements of the platen 502 and the polishing pad drum 504. According tovarious embodiments, the controller 526 and the drive assemblies 522 and524 cooperate to control the direction, speed and/or timing of themovements of the platen 502 and the polishing pad drum 504.

The illustrated CMP system 500 also includes a planarizing system 518for dressing the polishing pad drum 504. The controller 526 is alsocoupled to and in communication with the planarizing system 518 tocontrol the process of dressing the polishing pad drum 504.

FIG. 6 is a side view of the CMP system of FIG. 5, illustrating themotion of the drum and the platen. According to this system embodiment600, the relative linear movement 612 between the polishing pad drum 604and the platen 602 is attributable to the platen drive assembly 522 ofFIG. 5, which linearly moves the platen 602 with respect to the drum604. The rotational movement 616 is attributable by the drum driveassembly 524 of FIG. 5.

FIG. 7 is a block diagram of one CMP system embodiment. According tothis embodiment, the CMP system 700 includes a platen 702 and apolishing pad drum 704. The polishing pad drum 704 is adapted to belinearly and rotationally moved. A drum drive assembly 724 controls boththe linear movement the rotational movement of the polishing pad drum704. A controller 726 is coupled to and in communication with the drumdrive assembly 724. According to various embodiments, the controller 726and drum drive assembly 724 cooperate to control the direction, speedand/or timing of the movements of the polishing pad drum 704. Theillustrated CMP system embodiment also includes a planarizing system 718for dressing the polishing pad drum 704. The controller 726 is alsocoupled to and in communication with the planarizing system 718 tocontrol the process of dressing the polishing pad drum 704.

FIG. 8 is a side view of the CMP system of FIG. 7, illustrating themotion of the drum and the platen. According to this system embodiment800, the relative linear movement between the polishing pad drum 804 andthe platen 802 is accomplished by the drum drive assembly 724 of FIG. 7,which linearly moves the polishing pad drum 804 in the direction oflinear motion arrow 812 with respect to the platen 802. The rotationalmotion, represented by arrow 816, of the polishing pad drum 804 also isaccomplished by the drum drive assembly 724 of FIG. 7.

FIG. 9 is a block diagram of one CMP system embodiment. According tothis embodiment, the CMP system 900 includes a platen 902 and apolishing pad drum 904. The polishing pad drum 904 is adapted to berotationally moved. A drum drive assembly 924 controls the rotationalmovement of the polishing pad drum 904. A controller 926 is coupled toand in communication with the drum drive assembly 924. According tovarious embodiments, the controller 926 and drum drive assembly 724cooperate to control the direction, speed and/or timing of therotational movement of the polishing pad drum 904.

According to this embodiment, a platen drive assembly 922 controls thelinear and vertical movement of the platen 902. The term “verticalmovement” represents movement that is orthogonal to the linear movementand that provides the predetermined distance, or predetermined minimumdistance, between the platen 902 and the polishing pad drum 904 as theplaten 902 and the polishing pad drum 904 pass each other during thelinear movement. That is, there is a distance between the platen 902 andthe polishing pad drum 904, and this distance decreases during thelinear movement as the polishing pad drum 904 and the platen approacheach other until the predetermined minimum distance is achieved. Duringa CMP process, the polishing pad drum 904 contacts the wafer at thispoint. The term “vertical movement” is not intended to be limited to aparticular orientation.

This predetermined minimum distance is variable. Thus, the CMP processis capable of being performed on the various layers built on the waferduring the fabrication process. The platen drive assembly 922 is capableof controlling this predetermined minimum distance. One of ordinaryskill in the art will understand, upon reading and comprehending thisdisclosure, that the drum drive assembly 924 may be moved to control thepredetermined minimum distance between the platen 902 and the polishingdrum 904.

The illustrated CMP system embodiment 900 also includes a planarizingsystem 918 for dressing the polishing pad drum 904. The controller 926is also coupled to and in communication with the planarizing system 918to control the process of dressing the polishing pad drum 904. Thecontroller 926 vertically moves the wafer platen 902 to compensate forchanges in the diameter of the drum 904 caused by the dressingoperation. One of ordinary skill in the art will understand, uponreading and comprehending this disclosure, that in various embodiments,the controller 926 vertically moves the drum 904 and/or the platen 902to compensate for changes in the diameter of the drum 904 caused by thedressing operation.

FIG. 10 is a side view of the CMP system of FIG. 9, illustrating themotion of the drum and the platen. According to this system embodiment1000, the rotational motion, represented by arrow 1016, of the polishingpad drum 1004 is accomplished by the drum drive assembly 924 of FIG. 9.The relative linear movement between the polishing pad drum 1004 and theplaten 1002 is accomplished by the platen drive assembly 922 of FIG. 9,which linearly moves the platen 1002 in the direction of linear motionarrow 1012 with respect to the platen 1002. Furthermore, the verticalmovement that provides the predetermined minimum distance between thepolishing pad drum 1004 and the platen 1002 is accomplished by theplaten drive assembly 922 of FIG. 9, which moves the platen 1002 asrepresented by vertical motion arrow 1028 with respect to the platen1002.

FIG. 11 is a block diagram of one CMP system embodiment. According tothis embodiment, the CMP system 1100 includes a platen 1102 and apolishing pad drum 1104. The polishing pad drum 1104 is adapted to berotationally moved. A drive assembly 1130 controls the rotationalmovement of the polishing pad drum 1104. Additionally, the driveassembly 1130 is adapted to control the relative linear motion andvertical motion between the platen 1102 and the polishing pad drum 1104.As was pointed out above, this relative motion can be accomplishedeither by moving the platen 1102 or the polishing pad drum 1104. Thisrelationship is illustrated in FIG. 11 by the dotted line 1132 thatgroups the platen 1102 and polishing pad drum 1104. A controller 1126 iscoupled to or in communication with the drive assembly 1130. Accordingto various embodiments, the controller 1126 and the drive assembly 1130cooperate to control the direction, speed and/or timing of the variousmotions of the platen 1102 and the polishing pad drum 1104. Theillustrated CMP system embodiment 1100 also includes a planarizingsystem 1118 for dressing the polishing pad drum 1104. The controller1126 is also coupled to and in communication with the planarizing system1118 to control the process of dressing the polishing pad drum 1104.

FIG. 12 is a block diagram of another CMP system embodiment. Accordingto this embodiment, the CMP system 1200 includes a platen 1202 and apolishing pad drum 1204. The polishing pad drum 1204 is adapted to berotationally moved. A drive assembly 1230 controls the rotationalmovement of the polishing pad drum 1204. Additionally, the driveassembly 1230 is adapted to control the relative linear motion andvertical motion between the platen 1202 and the polishing pad drum 1204,as represented by the dotted line 1232. A controller 1226 is coupled toor in communication with the drive assembly 1230. According to variousembodiments, the controller 1226 and the drive assembly 1230 cooperateto control the direction, speed and/or timing of the various motions ofthe platen 1202 and the polishing pad drum 1204.

The illustrated CMP system embodiment 1200 also includes a planarizingsystem 1218 for dressing the polishing pad drum 1204 and a slurryapplicator 1234 for applying a slurry used in a CMP process. Thecontroller 1226 is also coupled to and in communication with theplanarizing system 1218 and the slurry applicator 1234 to control theprocess of dressing the polishing pad drum 1204 and the process ofapplying a slurry.

FIG. 13 is a block diagram of one embodiment of an electronic systemused as a controller for a CMP system. FIG. 13 is a simplified blockdiagram of a high-level organization of an electronic system 1326.According to one embodiment, the electronic system 1326 functions as acontroller in a CMP process. The electronic system 1326 has functionalelements, including an arithmetic/logic unit (ALU) or processor 1340, acontrol unit 1342, a memory device unit 1344, and an input/output (I/O)device 1346. Generally such an electronic system 1326 will have a nativeset of instructions that specific operations to be performed on data bythe ALU 1340 and other interactions between the ALU 1340, the memorydevice unit 1344 and the I/O devices 1346. The memory device unit 1344contains the data plus a stored list of instructions. The control unit1342 coordinates all operations of the processor 1340, the memory device1344 and the I/O devices 1346 by continuously cycling through a set ofoperations that cause instructions to be fetched from the memory device1344 and executed. These executed instructions include sending andreceiving signals such as control, communication, data and sensorsignals.

The figures presented and described in detail above are similarly usefulin describing the method aspects of the present subject matter. Themethods described below are nonexclusive as other methods may beunderstood from the specification and the figures described above.

FIG. 14 is a flowchart illustrating one embodiment of a semiconductorprocess that incorporates one embodiment of a CMP process. The processbegins at 1450. The pad, or polishing pad drum, is dressed at 1452 toensure that the drum has a planar surface. One method for dressing thepad uses a finely tuned laser beam.

Wafers are initially polished to achieve a planar surface upon which thevarious layers for each wafer are formed. As it is at this timeimpractical to achieve a completely parallel top surface with respect tothe bottom surface, the wafer may have a slight non planar top surfacewhen referenced to the bottom surface of the wafer. A normalsemiconductor process is run after the wafer is initially polished.

At 1454, the wafer is positioned or mounted on the platen such that itis capable of being positioned in a consistent position relative to theplaten each time that it is polished. The distance between the platenand the polishing pad drum is adjusted or set at 1456 so as toaccommodate the thickness of each successive layer built on the waferduring the fabrication process. This distance represents thepredetermined minimum distance between the platen and the polishing paddrum as the platen and polishing pad drum pass each other.

At 1458, the wafer is polished. The wafer is polished by rotating thepolishing pad drum at 1460 and by creating a linear movement between thedrum and the platen at 1462. After the polishing process, the wafer isremoved from the platen at 1464, and semiconductor fabrication processesare performed on the wafer at 1466. These semiconductor fabricationprocesses include, but are not limited to, processes that are used inthe damascene process described earlier in this disclosure in thesection entitled Background of the Invention.

After the semiconductor fabrication process, at 1468, it is determinedwhether the surface of the wafer is to be polished. For example, in thedamascene process, the wafer is polished after the copper is blanketdeposited. If the surface of the wafer is to be polished, the processproceeds to 1470 where it is determined whether the polishing pad drumshould be dressed again. If the drum should be dressed, the processproceeds back to 1452. If the drum does not need to be dressed, theprocess proceeds back to 1454. If, at 1468, it is determined that thesurface of the wafer is not to be polished, the process proceeds to 1472where it is determined whether another semiconductor process is to beperformed. If it is determined that another semiconductor process is tobe performed, then the process proceeds back to 1466. If it isdetermined that another semiconductor process is not to be performed,the process continues to 1474 where the semiconductor processterminates.

FIG. 15 is a flowchart illustrating one embodiment of a process forremoving a semiconductor layer. This process recognizes that a singlelayer often will have an uneven surface characterized with peaks. A passof the polishing pad with respect to the wafer removes the peaks, or aportion of the peaks. The peaks of the wafer surface may cause thepolishing pad to wear unevenly. As such, it may be desirable to dressthe pad between polishing passes. The removal of a single layer mayrequire several polishing passes and several dressings of the polishingpad.

According to the illustrated embodiment, the process for removing asemiconductor layer begins at 1580. The pad, or polishing pad drum, isdressed at 1582 to ensure that the drum has a planar surface. One methodfor dressing the pad uses a finely tuned laser beam. The distancebetween the platen and the polishing pad drum is adjusted or set at 1584so as to accommodate the thickness of each successive layer built on thewafer during the fabrication process. This distance represents thepredetermined minimum distance between the platen and the polishing paddrum as the platen and polishing pad drum pass each other.

At 1586, the wafer is polished. The wafer is polished by rotating thepolishing pad drum at 1588 and by creating a linear movement between thedrum and the platen at 1590. At 1592, it is determined whether thesurface of the wafer is to be polished again. If the surface of thewafer is to be polished, the process proceeds to 1594 where it isdetermined whether the polishing pad drum should be dressed again. Ifthe drum should be dressed, the process proceeds back to 1582. If thedrum does not need to be dressed, the process proceeds back to 1584. If,at 1592, it is determined that the surface of the wafer is not to bepolished, the process proceeds to 1596 where the process for removing asemiconductor layer terminates.

CONCLUSION

The present subject matter provides chemical mechanical polishing (CMP)systems and methods in which a rotating polishing pad drum is used topolish a surface of a wafer held by a platen. The polishing pad drumoperably contacts the wafer through a relative linear movement betweenthe wafer and the rotating polishing pad drum. The linear motion isperpendicular (albeit in a different plane) to the axis of rotation ofthe polishing pad drum. That is, the relative linear motion ischaracterized by a linear motion vector. A projection of this linearmotion vector into a parallel plane that contains the axis of rotationfor the polishing pad drum is perpendicular, or generally perpendicular,to the axis of rotation. The CMP systems and processes described hereinsignificantly increase the degree of long range planarization byreducing uniformity problems such as dishing and rounding of thefeatures. The result is that each polished layer has a surface orthickness that is substantially uniform through the layer.

The present subject matter provides chemical mechanical polishing (CMP)systems and methods that use a polishing pad drum. A platen holds awafer to be polished. The polishing pad drum has a generally cylindricalshape and rotates along an axis of the cylinder. According to oneembodiment, the platen linearly moves the wafer into contact with thepolishing pad drum. This linear motion is characterized as beingperpendicular or generally perpendicular (albeit in a different plane)to the axis of rotation of the polishing pad drum. In other words, thevector that represents the relative linear motion of the wafer withrespect to the polishing pad drum lies in a plane and can be projectedon a parallel plane that includes the axis of rotation of the polishingpad. This projection of the linear motion vector is perpendicular, orgenerally perpendicular, to the axis of rotation. This polishing systemis capable of significantly increasing the degree of long rangeplanarization by reducing uniformity problems such as dishing androunding of the features.

One aspect of the present subject matter is a polishing system. Onepolishing system embodiment includes a platen adapted to receive awafer, and a polishing pad drum that has a cylindrical, or generallycylindrical, shape with a length and an axis of rotation along thelength. The polishing pad drum and the platen are adapted to be operablypositioned a predetermined distance from each other in preparation topolish a surface of the wafer. The polishing pad drum is adapted torotate about the axis of rotation along the drum length. The polishingpad drum, the platen, or both the polishing pad drum and the platen areadapted to be linearly moved to polish the surface of the wafer usingthe rotating polishing pad drum.

According to one embodiment, the polishing system includes a controller,a platen adapted to receive a wafer, a polishing pad drum, and a driveassembly coupled to the controller. The controller and drive assemblycooperate with each other to rotate the polishing pad drum and tooperably move the polishing pad drum, the platen, or both the polishingpad drum and the platen to create a relative linear motion to polish thewafer.

According to one embodiment, the polishing system includes a controller,a platen adapted to receive a wafer, a polishing pad drum, a driveassembly coupled to the controller, and a trimming laser coupled to thecontroller. The controller and drive assembly along with the driveassembly for the laser are so controlled that the change in the diameterof the polishing drum, with the dressing operation, is accounted for inthe vertical positioning of the platen. Thus, a specified thickness ofmaterial may be precisely removed.

One aspect of the present subject matter is a method for planarizing awafer. According to this method, the wafer is positioned on a platen,and a polishing pad drum is rotated. A linear movement is createdbetween the polishing pad drum and the platen to polish the wafer.

One aspect of the present subject matter is a process. According to oneprocess embodiment, a polishing pad drum is dressed and a wafer ispositioned on a platen. The polishing pad drum and the platen are set tobe separated by a predetermined distance. This predetermined distanceprovides the desired separation between the wafer and the polishing paddrum for a polishing process. This predetermined distance may becharacterized as a predetermined minimum distance between the polishingpad drum and the platen as they pass each other. The wafer is polishedby rotating the polishing pad drum and creating a linear movementbetween the polishing pad drum and the platen. The wafer is removed fromthe platen, and a semiconductor fabrication process is performed on thewafer.

These and other aspects, embodiments, advantages, and features willbecome apparent from the following description of the invention and thereferenced drawings.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiment shown. This application isintended to cover any adaptations or variations of the presentinvention. It is to be understood that the above description is intendedto be illustrative, and not restrictive. Combinations of the aboveembodiments, and other embodiments will be apparent to those of skill inthe art upon reviewing the above description. The scope of the inventionincludes any other applications in which the above structures andfabrication methods are used. The scope of the invention should bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

1. A method for planarizing a wafer, comprising: positioning a wafer ona platen; rotating a polishing pad drum in a predetermined direction andspeed; and creating a linear movement having a predetermined directionand speed in at least one of three orthogonal axis between the polishingpad drum and the platen during an operation to polish the wafer.
 2. Themethod of claim 1, wherein rotating the polishing pad drum produces atangential force between the polishing pad drum and the platen, andwherein creating a linear movement between the polishing pad drum andthe platen includes creating a linear movement in the direction of thetangential force.
 3. The method of claim 1, wherein a rigid polishingpad forms the polishing pad drum.
 4. The method of claim 1, wherein alength of the polishing pad drum spans across the diameter of wafer topolish the wafer in one pass.
 5. The method of claim 1, further movingthe wafer and platen with respect to the polishing pad drum in adirection to throw debris in a direction toward a previously processedportion of the wafer.
 6. The method of claim 1, wherein creating alinear movement between the polishing pad drum and the platen includescontrolling at least one of a linear direction of the platen, and alinear speed of the polishing pad drum.
 7. The method of claim 1,wherein creating a linear movement between the polishing pad drum andthe platen includes providing a linear movement that has a projectedlinear motion vector on a parallel plane that contains an axis ofrotation for the polishing pad drum such that the projected linearmotion vector is generally perpendicular to the axis of rotation.
 8. Themethod of claim 1, further comprising setting a minimum distance toseparate the platen and the polishing pad drum when the platen and thepolishing pad drum pass each other.
 9. The method of claim 1, furthercomprising dressing the polishing pad drum with a planarizing system.10. The method of claim 9, wherein dressing the polishing pad drum witha planarizing system includes dressing the polishing pad drum with afinely tuned laser beam.
 11. The method of claim 1, further includingdispensing a polishing slurry on the wafer.
 12. The method of claim 1,further including providing the polishing pad drum with an embeddedpolishing abrasive.
 13. A method for planarizing a wafer, comprising:dressing a rigid polishing pad drum to obtain a uniform drum diameteralong a rotational axis of the drum; positioning at least one wafer in afixed position on a platen; setting a specified minimum distance toseparate a rotational axis of the polishing pad drum and a top surfaceof the platen when they pass each other; polishing the wafer by rotatingthe polishing pad drum in contact with the wafer and creating a linearmovement between the polishing pad drum and the wafer; removing thewafer from the platen; determining a planarity of the wafer andcomparing it to a specified value; and if the determined planarity ofthe wafer has not obtained at least the specified value, repeating themethod, and if the specified value has been obtained, performing asemiconductor fabrication process on the wafer.
 14. The method of claim13, wherein the polishing includes attaching a polishing pad havingembedded abrasive material to the rigid polishing pad drum.
 15. Themethod of claim 14, wherein dressing includes smoothing a surface of thepolishing pad with a laser.
 16. The method of claim 13, whereinpolishing includes adding a liquid slurry to at least one of thepolishing pad drum and wafer during at least a portion of a time periodof contact between the polishing pad drum and wafer.
 17. The method ofclaim 16, wherein polishing includes adding a material chemicallyreactive to a material on the wafer to the slurry.
 18. The method ofclaim 13, wherein polishing includes a length of the drum rotationalaxis exceeding a diameter of the wafer.
 19. The method of claim 18,wherein polishing includes setting the specified minimum distance toremove a desired thickness from a top surface of the wafer in a singlepass of the linear movement between the polishing pad drum and thewafer.
 20. The method of claim 18, wherein polishing includes setting atangential force between the polishing pad drum and the wafer to removea desired thickness from a top surface of the wafer in a single pass.21. The method of claim 13, wherein positioning includes placing twowafers on the platen with a line drawn between a center of each wafer isperpendicular to the rotational axis of the polishing pad drum.
 22. Themethod of claim 13, wherein polishing the wafer includes rotating thepolishing pad drum in contact with the wafer in a same direction as thelinear movement between the polishing pad drum and the wafer.
 23. Themethod of claim 18, wherein polishing the wafer further includes:determining a condition of the wafer after a single first pass of thelinear movement between the polishing pad drum and the wafer;determining if another single pass of polishing the wafer is required;dressing the rigid polishing pad drum to obtain a uniform drum diameteralong a rotational axis of the drum; resetting the specified minimumdistance between a rotational axis of the polishing pad drum and a topsurface of the platen to correct for a changed diameter of the drum;polishing the wafer in single second pass in a same direction as thefirst pass of the linear movement between the polishing pad drum and thewafer; and repeating until a determining that a specified result hasbeen obtained.
 24. A method of planarizing a wafer, comprising: dressinga polishing pad drum to obtain a uniform drum diameter along arotational axis of the drum; setting a specified distance to separatethe rotational axis of the polishing pad drum and a wafer attached to aplaten when they pass each other; polishing the wafer by rotating thepolishing pad drum and creating a linear movement between the rotationalaxis of the polishing pad drum and the platen when they contact eachother with a tangential force, and pass each other in a specifieddirection; determining whether the wafer is in a specified condition orneeds to be polished again; upon determining that the wafer is to bepolished again, determining whether the polishing pad is to be dressed;upon determining that the polishing pad is to be dressed, dressing thepolishing pad drum prior to polishing the wafer again in the specifieddirection; and upon determining that the polishing pad is not to bedressed, repolishing the wafer.
 25. The process of claim 24, whereindetermining whether the wafer is to be polished again is based onwhether further polishing is required to remove at least one of aspecified thickness and a specified semiconductor layer.
 26. The processof claim 24, wherein determining whether the polishing pad is to bedressed is based on whether the polishing pad has a uniform diameteralong a specified length of the rotational axis.